1. Field of the Invention
This invention relates to the field of data processing systems. More particularly, this invention relates to memory protection mechanisms within data processing systems using which it is determined from the target address of a memory access request what attributes are associated with that target address. As an example, in the case of a memory protection unit, depending upon the attributes associated with a particular target address, a memory access may be permitted or not permitted.
2. Description of the Prior Art
It is known to provide memory protection units which are programmable such that the total memory space is divided into programmable memory regions with programmable attributes associated with each of those memory regions. As an example, the attributes may indicate properties such as read only, cacheable, non-cacheable, not executable, etc. Circuit resources are consumed in the elements needed to define the programmable memory regions and to store the programmable attributes associated with those programmable memory regions. Whilst fine-grained control might be desirable, this requires significant circuit resources to achieve and this brings with it a disadvantageous increase in gate count, power consumption, cost etc.
It is an object of at least preferred embodiments of the invention to seek to provide suitably fine-grained control of memory accesses whilst consuming relatively low levels of circuit resource in a manner which is well suited to the most common type of use for such memory protection units.